The number of echoes combined into a single image or image set in multiple echo imaging sequences or echo-train techniques such as rapid acquisition with relaxation enhancement (RARE), fast-spin echo (FSE), and turbo spin-echo (TSE). In RARE imaging, the ETL typically equals the acceleration factor.
As for tooth pain, it is caused by a reaction of the nerves inside a tooth's pulp chamber with the severity dependent upon the type and degree of the stimulus. What follows are some examples of symptoms you may be feeling and their possible causes.
Sensitivity. Sensitivity can occur when the underlying layer of your teeth becomes exposed as a result of receding gum tissue. The roots of your teeth, which are not covered by protective hard enamel, contain thousands of tiny tubules leading to the tooth's nerve center (the pulp).When exposed, these tubules allow stimuli â such as hot or cold food â to stimulate the nerve in your tooth, causing the pain you feel.he roots of your teeth, which are not covered by protective hard enamel, contain thousands of tiny tubules leading to the tooth's nerve center (the pulp). When exposed, these tubules allow stimuli â such as hot or cold food â to stimulate the nerve in your tooth, causing the pain you feel.